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From: David Rowley <david.rowley@2ndquadrant.com>
Date: Mon, 13 May 2019 11:47:12 +1200
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 <CAKJS1f-1=BoVkJaTnfb87nrVUFLprdc7smsBsF5MGyCXnNivzw@mail.gmail.com>
Subject: Re: PostgreSQL 12: Feature Highlights
To: "Jonathan S. Katz" <jkatz@postgresql.org>
Cc: pgsql-advocacy@lists.postgresql.org
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On Mon, 13 May 2019 at 03:28, Jonathan S. Katz <jkatz@postgresql.org> wrote:
> - Performance, e.g. enhanced partition pruning, COPY performance, ATTACH

I don't think it's very accurate to say that the performance of
partition pruning has been improved. Really the improvement there is
due to the change in the order of operations, where we now perform
pruning before fetching partition meta-data. Pruning itself, I don't
believe became any faster in PG12. There were, however various tweaks
to improve performance of some operations around run-time partition
pruning both in the planner and during execution, these, however, are
not improvements to pruning itself, but more the operations around
setting up pruning and handling what happens after pruning takes
place. Bruce has now changed the release notes to mention "Improve
performance of many operations on partitioned tables", which seems
like a more accurate generalisation of what was improved, although, I
still think it's overly vague.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services